Heat exchanger

ABSTRACT

A heat exchanger includes tubes arranged in a stacking direction and a tank connected to the tubes. A tube of the tubes has a pair of flat portions having flat plate shapes facing each other, and a curved portion connecting ends of the pair of flat portions. The tank includes a plate having insertion holes into which the tubes are inserted, and container. The plate has a first portion along a longitudinal direction of the tubes, and a second portion extending from an end of the first portion toward the container. When the plate is viewed in the stacking direction, a boundary between the first portion and the second portion is shifted from a boundary between each of the pair of flat portions and the curved portion toward the pair of flat portions.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of International Patent Application No. PCT/JP2021/003457 filed on Feb. 1, 2021, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2020-023492 filed on Feb. 14, 2020. The entire disclosures of all of the above applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a heat exchanger that performs heat exchange between heat medium and air.

BACKGROUND

For example, a heat exchanger such as a radiator or an evaporator is provided with metal tubes through which a heat medium passes. The heat exchanger performs heat exchange between heat medium passing inside the tubes and the air passing outside the tubes.

SUMMARY

A heat exchanger according to the present disclosure is a heat exchanger for heat exchange between heat medium and air. This heat exchanger includes tubes arranged in a stacking direction and being tubular members inside which the heat medium flows, and a tank connected to the tubes. A tube of the tubes has a pair of flat portions having flat plate shapes facing each other, and a curved portion connecting ends of the pair of flat portions. A normal direction of each of the pair of flat portions is along the stacking direction. The tank has a plate having insertion holes into which the tubes are inserted, and a container defines a space for storing the heat medium. The plate has a first portion arranged such that a normal direction of the first portion is along a longitudinal direction of the tubes, and a second portion extending from an end of the first portion toward the container. The end of the first portion faces in an air flow direction in which the air flows. When the plate is viewed along the stacking direction, a boundary between the first portion and the second portion is shifted from a boundary between each of the pair of flat portions and the curved portion toward the pair of flat portions.

BRIEF DESCRIPTION OF DRAWINGS

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

FIG. 1 is a diagram illustrating an overall configuration of a heat exchanger according to a present embodiment.

FIG. 2 is an enlarged view showing a part of the heat exchanger of FIG. 1 .

FIG. 3 is a diagram illustrating fins included in the heat exchanger of FIG. 1 and tubes located above and below the fins.

FIG. 4 is a diagram illustrating a structure of a tube and an amount of strain generated at a joint of the tube.

FIG. 5 is a diagram illustrating a configuration of a plate included in the heat exchanger.

DETAILED DESCRIPTION

To begin with, examples of relevant techniques will be described.

A heat exchanger according to an example, tubes are often brazed to a metal plate in a state of being inserted into the metal plate forming a part of a tank. In the heat exchanger having the configuration, a strain tends to be generated at a joint between the tubes and the metal plate due to thermal expansion or thermal contraction depending on temperature of heat medium.

A wall thickness of the tubes needs to be relatively small so that heat exchange can be performed efficiently. Therefore, if the above-mentioned strain is generated at the joint between the tubes and the plate, a part of the tubes may be broken. Since each tube of the heat exchanger has a flat shape in cross-section, a breakage of the tube due to a strain is particularly likely to be generated at a boundary between a flat portion of the tube and a curved portion of the tube.

In contrast, according to one aspect of the present disclosure, a heat exchanger exchanges heat between heat medium and air. This heat exchanger includes tubes arranged in a stacking direction and being tubular members inside which the heat medium flows, and a tank connected to the tubes. A tube of the tubes has a pair of flat portions having flat plate shapes facing each other, and a curved portion connecting ends of the pair of flat portions. A normal direction of each of the pair of flat portions is along the stacking direction. The tank has a plate having insertion holes into which the tubes are inserted, and a container defines a space for storing the heat medium. The plate has a first portion arranged such that a normal direction of the first portion is along a longitudinal direction of the tubes, and a second portion extending from an end of the first portion toward the container. The end of the first portion faces in an air flow direction in which the air flows. When the plate is viewed along the stacking direction, a boundary between the first portion and the second portion is shifted from a boundary between each of the pair of flat portions and the curved portion toward the pair of flat portions.

The present inventors have conducted an experiment in a configuration in which the boundary between the first portion and the second portion of the plate is located at or shifted from the boundary between each of the pair of flat portions and the curved portion of the tubes toward the curved portion when the plate is viewed along the stacking direction. In this configuration, it has been found that a strain of the tube tends to be relatively large at the time of thermal expansion or thermal contraction.

This is because the boundary between the first portion and the second portion is considered to become a starting point of deformation of the plate during thermal expansion or contraction of the tubes. As a result, a strain due to the deformation is concentrated on the curved portion of the tube.

Therefore, in the heat exchanger of the present disclosure, when the plate is viewed along the stacking direction, the boundary between the first portion and the second portion is shifted from the boundary between each of the pair of flat portions and the curved portion toward the pair of flat portions. In the configuration, the flat portion instead of the curved portion of the tube is subjected to a stress caused by a deformation of the plate that occurs from the boundary between the first portion and the second portion. As a result, a maximum value of strain generated in the tube is capable of reducing compared with a conventional case.

According to the present disclosure, the heat exchanger which is capable of reducing a strain at a joint between the tube and the plate is provided.

Hereinafter, the present embodiments will be described with reference to the attached drawings. To facilitate understanding, identical constituent elements are assigned identical symbols in the drawings, and the duplicate descriptions on those will be omitted.

A heat exchanger 10 according to a present embodiment will be described. The heat exchanger 10 is a heat exchanger mounted on a vehicle (not shown). As shown in FIG. 1 , the heat exchanger 10 is a composite heat exchanger in which a radiator 100 and an evaporator 200 are combined and integrated.

The radiator 100 is a heat exchanger for cooling a high-temperature coolant water that has passed through a heating element (not shown) via heat exchange between the coolant water and air. The “heating element” here is a device mounted on a vehicle and requiring cooling, for example, an internal combustion engine, an intercooler, a motor, an inverter, or a battery. The evaporator 200 is a part of an air conditioner (not shown) mounted on the vehicle, and is a heat exchanger for evaporating a liquid phase refrigerant by heat exchange with air.

First, a configuration of the radiator 100 will be described. The radiator 100 includes tanks 110, 120, tubes 130, and fins 140. In FIG. 1 , the fins 140 are omitted.

The tanks 110, 120 are metal containers for temporarily storing a coolant water, which is a heat medium. Each of the tanks 110, 120 is a long and thin container having an approximately cylindrical pillar shape and arranged such that longitudinal directions of the tanks 110, 120 are along an up-down direction. The tanks 110, 120 are arranged at positions separated from each other in a horizontal direction, and the tubes 130 and the fins 140 are arranged between the tanks 110, 120.

A tank 110 of the tanks 110, 120 has a plate 300 and a container 400, and is formed by combining the plate 300 and the container 400 and brazing them to each other. The plate 300 is a flat plate-shaped member, and has insertion holes 301 into which the tubes 130 are inserted. The container 400 defines a space for storing the coolant water. An entire of a face of the container 400 facing the tubes 130 is an opening, and the opening is water-tightly closed by the plate 300.

As shown in FIG. 1 , the plate 300 constituting the tank 110 is also a part of a member constituting the tank 210 included in the evaporator 200. This configuration can be also considered as a configuration in which a plate 300 constituting the tank 110 and a plate 300 constituting the tank 210 are connected so as to be integrated.

Further, the container 400 constituting the tank 110 is also a part of a member constituting the tank 210. This configuration can be also considered as a configuration in which a container 400 constituting the tank 110 and a container 400 constituting the tank 210 are connected so as to be integrated.

In the above configuration, the tank 110 is integrated with the tank 210. Similarly, a tank 120 is integrated with a tank 220 by a configuration in which a plate 300 and a container 400 are joined to each other. FIG. 1 shows a state in which the container 400 is removed from the plate 300 in order to show internal configurations of the tank 110 and the tank 210.

The tank 110 has a receiving portion 111 and a receiving portion 112 for receiving the coolant water that has passed through the heating element. The receiving portion 111 is provided at a position in an upper part of the tank 110. The receiving portion 112 is provided at a position in a lower part of the tank 110.

As shown in FIG. 1 , an internal space of the tank 110 is divided into upper and lower parts by a separator S3. The coolant water from the receiving portion 111 flows into the upper part of the internal space of the tank 110 above the separator S3. The coolant water from the receiving portion 112 flows into the lower part of the internal space of the tank 110 below the separator S3.

The tank 120 has a discharge portion 121 and a discharge portion 122 for discharging the coolant water that has been subjected to heat exchange to the outside. The discharge portion 121 is provided at a position in an upper part of the tank 120. The discharge portion 122 is provided at a position in a lower part of the tank 120.

A separator similar to the separator S3 is arranged inside the tank 120 at the same height as the separator S3. The internal space of the tank 120 is divided into the upper and lower parts by the separator. The coolant water that has flowed into the internal space above the separator in the tank 120 is discharged to the outside from the discharge portion 121. The coolant water that has flowed into the internal space below the separator in the tank 120 is discharged to the outside from the discharge portion 122.

The tubes 130 are each a tubular member through which the coolant water passes, and the radiator 100 has the multiple tubes 130. Each tube 130 is an elongated straight tube and is arranged so as to extend along the horizontal direction. One end of the tube 130 is connected to the tank 110, and the other end is connected to the tank 120. Accordingly, the internal space of the tank 110 communicates with the internal space of the tank 120 through the tubes 130.

The tubes 130 are arranged in the up-down direction, that is, in the longitudinal direction of the tank 110. The fins 140 are each arranged between tubes 130 adjacent to each other in the up-down direction, but the fins 140 are not shown in FIG. 1 . A direction in which the tubes 130 are stacked, that is, the up-down direction in the present embodiment is hereinafter also referred to as a “stacking direction”.

The coolant water supplied from the outside to the tank 110 flows into the tank 120 through the tubes 130. When the coolant water passes through the inside of the tubes 130, the coolant water is cooled by the air passing outside the tubes 130 such that the temperature of the coolant water is lowered. A flow direction of the air is perpendicular to both the longitudinal direction of the tank 110 and a longitudinal direction of the tubes 130, and air flows from the radiator 100 to the evaporator 200. A fan (not shown) for sending air in the flow direction is provided in the vicinity of the heat exchanger 10.

Each fin 140 is a corrugated fin formed by bending a metal plate in a wavy shape. As described above, the fin 140 is arranged at a position between tubes 130 adjacent to each other in the up-down direction. That is, in the radiator 100, the fins 140 and the tubes 130 are stacked so as to be alternately arranged in the stacking direction. FIG. 2 is an enlarged view showing the fin 140 and configurations in the vicinity of the fin 140, when the radiator 100 is viewed along the air flow direction. As shown in FIG. 2 , peaks of the wavy fin 140 are in contact with and brazed to surfaces of the tubes 130 adjacent to each other in the stacking direction.

When the coolant water passes inside the tubes 130, the heat of the coolant water is transferred to the air through the tubes 130 and also to the air through the tubes 130 and the fins 140. That is, a contact area with the air is increased by the fins 140, thereby the heat exchange between the air and the coolant water is efficiently performed.

The configuration of the evaporator 200 will be described with reference to FIG. 1 . The evaporator 200 includes tanks 210, 220, tubes 230, and fins 140.

The tanks 210, 220 are containers for temporarily storing refrigerant, which is a heat medium. Each of the tanks 110, 120 is a long and thin container having an approximately cylindrical pillar shape and arranged such that longitudinal directions of the tanks 110, 120 are along an up-down direction. The tanks 210, 220 are arranged at positions separated from each other in the horizontal direction, and the tubes 230 and the fins 140 are arranged between the tanks 210, 220.

The tanks 210, 220 have the similar configuration as the tanks 110, 120 described above. As described above, the tank 210 is integrated with the tank 110 of the radiator 100. The plate 300 and the container 400 are joined to each other to form the tank 210. Similarly, the tank 220 is integrated with the tank 120 of the radiator 100. The plate 300 and the container 400 are joined to each other to form the tank 220.

The tank 210 has a receiving portion 211 and a discharge portion 212. The receiving portion 211 receives the refrigerant circulating in the air conditioner. The receiving portion 211 is supplied with a low-temperature liquid-phase refrigerant that has passed through an expansion valve (not shown) provided in the air conditioner. The receiving portion 211 is provided at a position near an upper end of the tank 210. The discharge portion 212 discharges the refrigerant that has been subjected to heat exchange to the outside. The gas phase refrigerant evaporated by heat exchange in the evaporator 200 is discharged to the outside from the discharge portion 212, and then supplied to a compressor (not shown) of the air conditioner. The discharge portion 212 is provided at a position near a lower end of the tank 210.

As shown in FIG. 1 , an internal space of the tank 210 is divided into three parts by separators S1, S2 in the up-down direction. The receiving portion 211 is provided at a position above an upper separator S1. The discharge portion 212 is provided at a position below a lower separator S2.

An internal space of the tank 220 is divided into upper and lower parts by a separator (not shown). The position of the separator is lower than the upper separator S1 and higher than the lower separator S2.

The tubes 230 are each a tubular member through which the refrigerant passes, and the evaporator 200 has the multiple tubes 230. Each tube 230 has an elongated straight shape and is arranged so as to extend in the horizontal direction. One end of the tube 230 is connected to the tank 210, and the other end is connected to the tank 220. Accordingly, the internal space of the tank 210 communicates with the internal space of the tank 220 through the tubes 230.

The tubes 230 are arranged in the up-down direction, that is, the stacking direction. In the present embodiment, each tube 230 is arranged adjacent to a tube 130 in the air flow direction. That is, the number of the tubes 230 is the same as the number of the tubes 130, and the tubes 230 are arranged at the same height as the tubes 130.

The refrigerant supplied from the outside to the receiving portion 211 flows into the upper part of the internal space of the tank 210 above the separator S1. The refrigerant passes inside tubes 230 arranged above the separator S1 and flows into the upper part of the internal space of the tank 220 above the non-illustrated separator. After that, the refrigerant passes inside tubes 230 arranged above the separator and below the separator S1 and flows into an internal space of the tank 210 between the separator S1 and the separator S2.

Further, after that, the refrigerant passes inside tubes 230 arranged above the separator S2 and below the separator in the tank 220, and flows into the lower part of the internal space of the tank 220 below the separator. The refrigerant passes inside tubes 230 arranged below the separator S2, flows into the lower part of the internal space of the tank 220 below the separator S2, and then is discharged to the outside from the discharge portion 212.

When passing inside each tube 230 as described above, the refrigerant is heated and evaporated by the air passing outside the tube 230, and changes from a liquid phase to a gas phase. The air has passed through the radiator 100 and the temperature of the air has been raised. The temperature of the air is lowered since the heat of the air is absorbed by the refrigerant when the air passes outside the tube 230.

A fin 140 (not shown in FIG. 1 ) is arranged between tubes 230 adjacent to each other in the stacking direction. The fin 140 is included in the radiator 100 described above. As shown in FIG. 3 , each fin 140 is arranged so as to extend from a position between the tubes 130 of the radiator 100 to a position between the tubes 230 of the evaporator 200. That is, each fin 140 is shared by the radiator 100 and the evaporator 200.

Therefore, the fins 140 and the tubes 230 are stacked so as to be alternately arranged in the stacking direction, in the evaporator 200, as in the radiator 100 described with reference to FIG. 2 . The peaks of the wavy fin 140 are in contact with and brazed to surfaces of tubes 230 adjacent to each other in the stacking direction.

When the refrigerant passes inside the tubes 230, the heat of the air is transferred to the refrigerant through the tubes 230 and also to the refrigerant through the tubes 230 and the fins 140. That is, a contact area with the air is increased by the fins 140, thereby the heat exchange between the air and the refrigerant is efficiently performed.

In the present embodiment, the heat of the coolant water passing through the inside of the tube 130 is further transferred to the refrigerant passing through the inside of the tube 230 by heat conduction through the fin 140. In the evaporator 200, not only the heat from the air but also the heat from the coolant water is recovered, so that the operating efficiency of the air conditioner is further improved.

As shown in FIG. 1 , a reinforcing plate 11, which is a plate-shaped member, is positioned upward of tubes 130, 230 which are located uppermost among the tubes 130, 230. Further, a reinforcing plate 12, which is a plate-shaped member, is positioned downward of the tubes 130, 230 which are located lowermost among the tubes 130, 230. The reinforcing plates 11, 12 is a metal plate provided to reinforce the tube 130 and the like to restrict their deformation.

In FIG. 1 , the flow direction of air is represented by a positive x-direction from the radiator 100 to the evaporator 200, and an x-axis is set along the flow direction of air. Further, a y-direction perpendicular to the positive x-direction is set from the tank 120 to the tank 110, that is, the longitudinal direction of the tubes 130, and a y-axis is set along the longitudinal direction of the tubes 130. Further, a z-direction perpendicular to both the positive x-direction and the y-direction is set from the lower side to the upper side, that is, the longitudinal direction of the tank 110, and the z-axis is along the longitudinal direction of the tank 110. Hereinafter, the description will be given using the positive x-direction, y-direction, and z-direction.

FIG. 3 shows one fin 140 and cross sections of tubes 130, 230 arranged on the upper and lower sides of the fin 140. As shown in FIG. 3 , each of the tubes 130, 230 has a flat cross section extending in the positive x-direction. A flow path FP1 through which the coolant water passes is formed inside each tube 130. An inner fin IF1 is arranged in the flow path FP1. Similarly, a flow path FP2 through which the refrigerant passes is formed inside each tube 230. An inner fin IF2 is arranged in the flow path FP2. A gap is formed between a tube 130 and a tube 230 arranged at the same height.

As shown in FIG. 2 and FIG. 3 , louvers 141 are formed on a fin 140. Each louver 141 is formed by cutting and bending a part of the fin 140. More specifically, multiple linear notches extending in the z-direction are formed on a flat portion of the fin 140 so as to be arranged in the positive x-direction, and then an area between two of the notches adjacent to each other is bent to form the louver 141. Since air passes through a gap formed in the vicinity of the louver 141, heat exchange between the air and the louver 141 is performed more efficiently. A shape of a louver formed on a conventional fin can be adopted as the shape of the louver 141.

A specific configuration of a tube 130 will be described with reference to FIG. 4 . As shown in FIG. 4 , the tube 130 is a tubular member formed by bending one metal plate, and then brazing end portions of the metal plate each other. As already mentioned, the tube 130 has a flat cross section extending in the positive x-direction. In the cross section, the tube 130 has a flat portion 131 and a curved portion 132.

The flat portion 131 is a portion formed in a flat plate shape, and is arranged so that a normal line of the flat portion 131 is along the z-axis. In other words, each tube 130 is arranged so that the normal direction of the flat portion 131 is along the stacking direction. The tube 130 has two flat portions 131. The two flat portions 131 are arranged facing each other in the up-down direction. In other words, the two flat portions 131 is a pair of flat plate-shaped portions facing each other in the tube 130.

The curved portion 132 is a portion connecting ends of the two flat portions 131 vertically arranged. The tube 130 has two curved portions 132. One of the two curved portions 132 is provided on a side of the flat portions 131 facing in the positive x-direction, and the other of the two curved portions 132 is provided on a side of the flat portions 131 facing in a negative x-direction. Dotted lines DL1, DL2 shown in FIG. 4 are boundaries between the flat portions 131 and the curved portions 132.

In the present embodiment, a shape of the curved portion 132 facing in the positive x-direction and a shape of the curved portion 132 facing in the negative x-direction are not the same as each other. Instead of the above configuration, shapes of the curved portions 132 may be the same as each other and be symmetrical about a y-z plane. More specifically, for example, the shapes of the curved portions 132 on both sides of the tube 130 in the x direction may be curved in an arc shape like the one curved portion 132 of the present embodiment facing in the positive x-direction, and may not have a crimped portion unlike the other curved portion 132 of the present embodiment facing in the negative x-direction. This tube 130 may be integrally formed as a whole by, for example, extrusion molding.

Since a shape of a tube 230 is substantially the same as the shape of the tube 130 as described above, the specific illustration of the shape of the tube 230 will be omitted. A portion of the tube 230 corresponding to the flat portion 131 is hereinafter referred to as a “flat portion 231”. Similarly, a portion of the tube 230 corresponding to the curved portion 132 is hereinafter referred to as a “curved portion 232”.

A graph shown in a lower portion of FIG. 4 schematically shows an amount of strain generated at a joint between the tube 130 and the plate 300 when thermal expansion occurs in the tube 130. The above-mentioned “joint” is a portion of the tube 130 that is joined to an edge of the insertion hole 301.

The strain described above occurs when the tube 130 expands or contracts depending on a temperature of the heat medium in a state of the tube 130 being brazed and fixed to the plate 300. For example, when high-temperature coolant water passes inside the tube 130 and low-temperature refrigerant passes inside the tube 230, the plate 300 is deformed due to the difference in degree of thermal expansion between the tube 130 and the tube 230. This deformation of the plate 300 causes a strain at the joint between the tube 130 and the plate 300. When the temperature of the coolant water is different in each of the tubes 130, a strain is also caused by the difference in degree of thermal expansion of each tube 130. Similar strain may be generated not only at the joint of the tube 130 but also at a joint of the tube 230.

As shown in FIG. 4 , the strain generated at the joint tends to be the largest at positions of the boundaries indicated by the dotted lines DL1, DL2. This is because the curved portions 132 have a large rigidity in the tube 130 and a stress at the time of thermal expansion or the like is considered likely to be concentrated on the curved portions 132. Therefore, a breakage of the tube 130 due to the strain tends to occur particularly easily at the above-described boundaries or in portions of the tube 130 shifted from the boundaries toward the curved portions 132. This tendency is also true for the tube 230.

Therefore, the heat exchanger 10 according to the present embodiment is capable of reducing the above-mentioned strain and preventing breakage of the tubes 130, 230 by devising the shape of the plate 300.

The shape of the plate 300 will be described with reference to FIG. 5 . FIG. 5 is a cross-sectional view showing the configuration of the plate 300 included in the tank 110, 210 and its vicinity. In FIG. 5 , the container 400 is not shown. Since a shape of the plate 300 included in the tank 120, 220 is the same as the shape of the plate 300 shown in FIG. 5 , descriptions of the plate 300 will be omitted.

As shown in FIG. 5 , the plate 300 has first portions 310, second portions 320, third portions 330, a fourth portion 340, and fifth portions 350.

Each first portion 310 is formed in a substantially flat plate shape. A normal direction of the first portion 310 is along the longitudinal direction of the tubes 130, that is, the y-direction. The plate 300 has two first portions 310. The two first portions 310 are arranged such that a central position of the plate 300 is interposed between the two first portions 310 along the x-axis. One of the two first portions 310 formed at a position shifted from the central position in the negative x-direction has insertion holes 301 into which the tubes 130 are inserted. Another of the two first portions 310 formed at a position shifted from the central position in the positive x-direction has insertion holes 301 into which the tubes 230 are inserted.

Although each first portion 310 is formed in a substantially flat plate shape as described above, the first portion 310 does not need to be a perfectly flat plate shape. For example, a portion in the vicinity of the insertion holes 301 may have been subjected to a burring process, and the processed portion may locally protrude toward a positive y-direction or a negative y-direction.

The second portions 320 extend from ends of the first portions 310 toward the container 400, that is, the positive y-direction. The ends of the first portions 310 face in the air flow direction. Both ends of each first portion 310 facing in the positive x-direction and the negative x-direction are provided with second portions 320. In FIG. 5 , dotted lines DL11, DL12 are each a boundary between a first portion 310 and two second portions 320 adjacent to the first portion 310. A most part of each insertion hole 301 is formed within the first portion 310, but another part of the insertion hole 301 overlaps with the second portion 320.

A second portion 320 provided at a position shifted from a first portion 310 in the positive x-direction is inclined so as to extend in a direction of a vector that is a sum of a vector in the positive y-direction and a vector in the positive x-direction. Another second portion 320 provided at a position shifted from the first portion 310 is inclined so as to extend in a direction of a vector that is a sum of a vector in the positive y-direction and a vector in the negative x-direction side.

The third portions 330 extend in the positive y-direction from two second portions 320 provided in a center part of the plate 300 among all the four second portions 320. Each third portion 330 extends straight from an end of a second portion 320. The end of the second portion 320 faces away from a first portion 310 joined to the second portion 320. The third portion 330 extends straight in the normal direction of the first portion 310. The third portion 330 has a flat plate shape. A flat surface of the third portion 330 facing inward of the tank 110, 120 is in contact with and joined to the container 400. In FIG. 5 , dotted lines DL13 are each a boundary between the second portion 320 and the third portion 330.

The fourth portion 340 is curved so as to connect ends of the two third portions 330. The ends of the two third portions 330 are facing away from the second portions 320. That is, the fourth portion 340 connects the ends of the two third portions 330 that face in the positive y-direction. The plate 300 is bent in an arc shape at the fourth portion 340. In FIG. 5 , a dotted line DL14 is a boundary between the third portions 330 and the fourth portion 340.

As shown in FIG. 5 , the two third portions 330 and the fourth portion 340 therebetween connect a part of the plate 300 included in the radiator 100 and a part of the plate 300 included in the evaporator 200, and function as a part that unifies the respective parts of the plate 300. Hereinafter, the two third portions 330 and the fourth portion 340 therebetween are also referred to as “connecting portion 360”.

In the heat exchanger 10 constructed as a composite heat exchanger, the radiator 100 including the tank 110, the tank 120, the tubes 130, and the fins 140 corresponds to a “first exchanger”. The coolant water passing through the first exchanger corresponds to a “first heat medium”. The evaporator 200 including the tank 210, the tank 220, the tubes 230, and the fins 140 corresponds to a “second exchanger”. The refrigerant passing through the second exchanger corresponds to a “second heat medium”. In the heat exchanger 10, the first exchanger and the second exchanger are arranged in the air flow direction, and the part of the plate 300 included in the first exchanger and the part of the plate 300 included in the second exchanger are connected so as to be integrated via the connecting portion 360 described above.

The fourth portion 340 is continuous in an entire area of the connecting portion 360 of the present embodiment in the z-direction. Instead of such an embodiment, the fourth portion 340 may be discontinuous at one or more locations in the z-direction.

The fifth portions 350 extend in the positive y-direction from two second portions 320 provided in outer parts of the plate 300 along the x-axis among all the four second portions 320. Each fifth portion 350 extends straight from an end of a second portion 320. The end of the second portion 320 faces away from a first portion 310 joined to the second portion 320. The fifth portion 350 extends straight in the normal direction of the first portion 310.

The fifth portion 350 is arranged to face the third portion 330 in the air flow direction. A flat surface of the fifth portion 350 facing inward of the tank 110, 210 is in contact with and joined to the container 400. In other words, the fifth portion 350 extends in the normal direction of the first portion 310 such that the fifth portion 350 and the third portion 330 face each other in the air flow direction and are joined to the container 400. In FIG. 5 , dotted lines DL15 are each a boundary between the second portion 320 and the fifth portion 350.

In FIG. 5 , the tubes 130 inserted into the insertion holes 301 of the plate 300 is also shown. Dotted lines DL21 and dotted lines DL22 are each a boundary between the flat portion 131 and the curved portion 132 or a boundary between the flat portion 231 and the curved portion 232, like the dotted line DL1 and the dotted line DL2 in FIG. 4 .

As shown in FIG. 5 , when the radiator 100 is viewed in the stacking direction, that is, viewed in the z-direction, the boundary DL11, DL12 between the first portion 310 and the second portion 320 is shifted from the boundary DL21, DL22 between the flat portion 131 and the curved portion 132 toward the flat portion 131. Similarly, when the evaporator 200 is viewed in the stacking direction, that is, viewed in the z-direction, the boundary DL11, DL12 between the first portion 310 and the second portion 320 is shifted from the boundary DL21, DL22 between flat portion 231 and the curved portion 232 toward the flat portion 231.

The present inventors have conducted an experiment in a configuration in which the boundary between the first portion 310 and the second portion 320 of the plate 300 is located at or shifted from the boundary between each of the pair of flat portions 131 and the curved portion 132 of the tubes 130 toward the curved portion 132 when the plate 300 is viewed along the stacking direction as shown in FIG. 5 . In this configuration, it has been found that a strain of the tube 130 tends to be relatively large at the time of thermal expansion or thermal contraction. Similarly, the boundary between the first portion 310 and the second portion 320 is located at or shifted from the boundary between each of the pair of flat portions 231 and the curved portion 232 of the tubes 230 toward the curved portion 232. In this configuration, it has been found that a strain of the tube 230 tends to be relatively large at the time of thermal expansion or thermal contraction.

This is because the boundary between the first portion 310 and the second portion 320 is considered to become a starting point of deformation of the plate 300 during thermal expansion or contraction of the tubes 130. As a result, a strain due to the deformation is concentrated on the curved portion 132 of the tubes 130 and the curved portion 232 of the tubes 230.

Contrary to this, in the radiator 100 of the heat exchanger 10 of the present embodiment, when the plate 300 is viewed in the stacking direction, the boundary between the first portion 310 and the second portion 320 is shifted from the boundary between the flat portion 131 and the curved portion 132 toward the flat portion 131. Similarly, in the evaporator 200, the boundary between the first portion 310 and the second portion 320 is shifted from the boundary between the flat portion 231 and the curved portion 232 toward the flat portion 231.

In this configuration, the flat portion 131, 231 instead of the curved portion 132, 232 is subjected to a stress caused by deformation of the plate 300 that occurs at the boundary between the first portion 310 and the second portion 320. As a result, strain can be diffused over a wide range of the joint, so that a maximum value of the strain generated in the tubes 130, 230 is capable of being reduced as compared with a conventional case. The above-mentioned “maximum value of strain” is the peak values of strain shown in the graph in FIG. 4 .

In the present embodiment, the connecting portion 360 is formed so that a gap between the two third portions 330 adjacent to each other is approximately zero. Therefor, the radiator 100 and the evaporator 200 are arranged adjacent to each other, and a length of the fins 140 in the positive x-direction is relatively short. As a result, heat conduction between the coolant water and the refrigerant via the fins 140 is efficiently performed, but on the contrary, a strain due to thermal expansion or the like of the tubes 130, 230 is large as compared with a case where the fins 140 are long.

However, in the present embodiment, the strain at the joint can be reduced by devising the shape of the plate 300 as described above. Therefore, even in a configuration where the fins 140 are shortened in consideration of heat conduction, breakage due to the strain of the tubes 130 or the like can be prevented.

By the way, a deformation of the plate 300 caused by thermal expansion or the like of the tubes 130, 230 begins at the boundary between the first portion 310 and the second portion 320 as described above. For example, the plate 300 is likely to begin the deformation at the boundary shown by the dotted line DL11 in FIG. 5 such that the second portion 320 inclines in the positive x-direction or the negative x-direction. In the present embodiment, the shape of the second portion 320 is devised so that most of the deformation can be absorbed by the second portion 320 and an influence on the joint between the tube 130 and the plate 300 can be reduced.

As shown in FIG. 5 , the second portion 320 has an overall shape that is substantially arcuately curved so as to be convex toward an outside of the tank 110. However, in a portion with the reference numeral “320” in FIG. 5 , the second portion 320 locally protrudes toward an inside of the tank 110. Hereinafter, the portion locally protruding toward the inside of the tank 110 is also referred to as a “bent portion 321”. One bent portion 321 is formed in each of four second portions 320. A position of the bent portion 321 in the second portion 320 does not overlap with the joint to the tube 130. Specifically, the bent portion 321 is shifted from a tip of the tube 130 toward the container 400.

Since the bent portion 321 is formed, the second portion 320 is provided with a function as a “leaf spring” that absorbs a strain. Since the second portion 320 including the bent portion 321 is easily deformed as a whole, a concentration of a strain due to thermal expansion on the joint of the tubes 130, 230 can be prevented. As a result, the maximum value of strain can be further reduced. As described above, in the present embodiment, since the bent portion 321 protrudes toward the inside of the tank 110 in the second portion 320, a strain is further reduced.

A radius of curvature of the bent portion 321 may be larger than a radius of curvature of the fourth portion 340. The “radius of curvature” in this case is a radius of curvature on a surface protruding and facing outside in an arc shape in the cross section as shown in FIG. 5 .

In the present embodiment, inner surfaces of the third portion 330 and the fifth portion 350 facing inward of the tank 110, 210 are in contact and brazed with the container 400. As shown in FIG. 5 , when a length of the inner surface of the third portion 330 in the y-direction is “L1” and a length of the inner surface of the fifth portion 350 in the y-direction is “L2”, the dimensions of each part of the heat exchanger 10 are set so that L1<L2. The “length in the y-direction” in the above corresponds to a length in the normal direction of the first portion 310.

Due to the structure of the plate 300, the rigidity near a central portion where the connecting portion 360 is formed is relatively high, while the rigidity near an end portion where the fifth portion 350 is formed is relatively low. Therefore, in the present embodiment, L1<L2 is set as described above, and a joint area in the fifth portion 350 is made larger than a joint area in the third portion 330. As a result, the rigidity in the vicinity of the end portion where the fifth portion 350 is formed can be increased, so that a balance of the rigidity of each portion of the plate 300 can be equalized. As a result, the maximum value of strain occurred in the plate 300 is capable of being further reduced.

As described above, in the present embodiment, the maximum strain is capable of being reduced by making the length of the fifth portion 350 in the normal direction of the first portion 310 longer than the length of the third portion 330 in the same direction. The length L1 of the third portion 330 in the normal direction of the first portion 310 may be 0.8 mm or more.

Further, the entire of the third portion 330 and the entire of the fifth portion 350 may be shifted from the tips of the tubes 130, 230 toward the container 400. That is, the third portion 330 and the fifth portion 350 may be arranged at positions so that the tubes 130, 230 are not interposed between the third portion 330 and the fifth portion 350.

In the above descriptions, an example of the case where the heat exchanger 10 is a composite heat exchanger in which the radiator 100 and the evaporator 200 are combined has been described. However, a device for reducing strain as described above can also be applied to a single heat exchanger that is not a composite type. For example, in the case of a single heat exchanger 10 composed of only the radiator 100, the plate 300 may be formed to have only the first portion 310, the second portion 320, the third portion 330, and the fifth portion 350 which are shown in an area shifted in the negative x-direction from the central position of the plate 300 in FIG. 5 .

The present embodiment have been described above with reference to specific examples. However, the present disclosure is not limited to those specific examples. Those specific examples that are appropriately modified in design by those skilled in the art are also encompassed in the scope of the present disclosure, as far as the modified specific examples have the features of the present disclosure. Each element included in each of the specific examples described above and the arrangement, condition, shape, and the like thereof are not limited to those illustrated, and can be changed as appropriate. The combinations of elements included in each of the above described specific examples can be appropriately modified as long as no technical inconsistency occurs. 

1. A heat exchanger for heat exchange between heat medium and air, the heat exchanger comprising: tubes arranged in a stacking direction and being tubular members inside which the heat medium flows; and a tank connected to the tubes, wherein a tube of the tubes has a pair of flat portions having flat plate shapes facing each other, and a curved portion connecting ends of the pair of flat portions, a normal direction of the pair of flat portions is along the stacking direction, the tank has a plate having insertion holes into which the tubes are inserted, and a container defines a space for storing the heat medium, the plate has a first portion arranged such that a normal direction of the first portion is along a longitudinal direction of the tubes, and a second portion extending from an end of the first portion toward the container, the end of the first portion faces in an air flow direction in which the air flows, and when the plate is viewed in the stacking direction, a boundary between the first portion and the second portion is shifted from a boundary between each of the pair of flat portions and the curved portion toward the pair of flat portions.
 2. The heat exchanger according to claim 1, wherein the tubes and the tank include: a first exchanger that performs heat exchange between a first heat medium and the air; and a second exchanger that performs heat exchange between a second heat medium and the air, the first exchanger and the second exchanger are arranged in the air flow direction, the plate is one of plates, and one of the plates provided in the first exchanger and another of the plates provided in the second exchanger are adjacent two plates and connected to be integrated to each other via a connecting portion.
 3. The heat exchanger according to claim 2, wherein the connecting portion includes: two third portions extending from, respectively, ends of second portions of the adjacent two plates, the ends of second portions facing away from first portions of the adjacent two plates, the two third portions extending in normal directions of the first portions; and a fourth portion that is curved so as to connect ends of the two third portions, the ends of the two third portions facing away from the second portions of the adjacent two plates.
 4. The heat exchanger according to claim 3, wherein lengths of the two third portions in the normal directions of the first portions are 0.8 mm or more.
 5. The heat exchanger according to claim 3, wherein each of the adjacent two plates has a fifth portion extending in the normal direction of the first portion, the fifth portion faces one of the two third portions in the air flow direction, and the fifth portion and the two third portions are joined to the container.
 6. The heat exchanger according to claim 5, wherein a length of the fifth portion in the normal direction of the first portion is longer than lengths of the two third portions in the normal direction of the first portion.
 7. The heat exchanger according to claim 1, wherein the second portion has a bent portion protrudes toward an inside of the tank. 